The present invention relates to a hydraulically operated impacting device which includes a casing having chambers, spaces and ducts for a pressurized medium, as well as a piston chamber for receiving reciprocating differential pistons to be used as actuating impact devices for the transmission of impact energy upon an impacting shifting or percussion tool. Moreover, the particular device to which the invention pertains includes a control valve being of sleevelike construction without transverse bore, and arranged concentrically-axially to the impacting or striking piston, the valve being hydraulically movable in one direction, but operated and displaced by the impact piston in the opposite direction.
German printed patent application 2,517,213 discloses a hydraulically operated impacting or striking device having a control valve which is displaced in one direction as stated by the moving piston and responds to the motion of the piston in the opposite direction, whereupon it is actuated by the pressurized fluid of the system such that it is moved in the opposite direction under the hydrostatic pressure of that medium. This particular device has the control valve arranged on the side facing the impact or percussion tool. This arrangement is disadvantaged by the fact that during the entire working stroke, it will be necessary to move the valve as a whole, i.e., one has to move its mass. This of course is detrimental with regard to the acceleration imparted upon the impact piston. Moreover, the control valve will in fact travel a longer path back than the operating piston. This means on the one hand that it has to be separated from the piston, which is an event that occurs differently for different objects to be impacted and struck, and for relatively soft objects this retraction may not even be possible. As a consequence, the control valve and the impact piston may desynchronize. On the other hand, the aforementioned longer travel path of the control valve requires means that it be captured. This means in turn an undue heating of the hydraulic medium. Moreover, the switching of the control valve requires under such circumstances an unduly high or large volume of pressure fluid such as oil.
In order to obtain the requisite chambers for returning the valve, it is guided on the inside as well as on the outside. Tight manufacturing tolerances are required here, and that entails considerable cost. Moreover, an arrangement of the control valve on the side of the impacting tool leads to transverse motion of the impact piston, and in the case of a noncentrical impacting upon the impacting tool, the wear is considerably high. Another disadvantage is the mechanical engagement between impacting piston and control valve, which also leads to a high wear and destruction of control edges involved, which in turn impedes the switchover operation.